DPlot

I have an linear x, y scatter plot. And I am trying to fit a Logarithmic curve to the data. How is this done?

The Polynomial Curve Fit command on the Generate menu will (in most cases) use an equation form that matches the scaling on the axes. For example for linear X, linear Y you'll get

y=C0+C1*x+C2*x^2+....

For linear x, logarithmic y you'll get

log10(y)=C0+C1*x+C2*x^2+....

and for logarithmic x, linear y you'll get

y=C0+C1*log10(x)+C2*(log10(x))^2+...

So if that's the form you want, right-click on the graph and select "Logarithmic X, Linear Y".

I have searched these forums but I can't find an answer to this. This thread is as close as I've found.

Is there a way to do a natural log curve (base e) instead of a log base 10?

If your plot's scaling is set to Linear X, Logarithmic Y, then Generate>Polynomial Curve Fit gives you both.

For example:

log(y) = C(0) + C(1)*x + C(2)*x^2 + ...
(log() = common logarithm)
Coefficients
C(00) = 0.346914605862
C(01) = -1.64979805157
C(02) = 3.25720861427

or

ln(y) = D(0) + D(1)*x + D(2)*x^2 + ...
(ln() = natural logarithm)
Coefficients
D(00) = 0.7988004
D(01) = -3.7988004
D(02) = 7.5

On the other hand if you're looking for base e scaling - no, sorry, that isn't in there.